Optical nano-antennas are kinds of optical devices that receive light and convert the received light into an electromagnetic field or perform an opposite function thereto. Radio waves used for mobile phone communication have a wavelength of approximately several cm. Thus, antennas for mobile phone communication have a certain degree of size. However, a wavelength of light is as extremely low as approximately 500 nm. For this reason, optical nano-antennas have to be made as thin as approximately 100 nm, which is a hundred-thousandth the thickness of human hair. It is possible to manufacture such minute antennas in accordance with the development of nanotechnology. However, there is a limitation that the antennas formed of nanoparticles can transmit and receive only light having a single wavelength. Thus, optical nano-antennas of the related art are not so effective to function as transmitters-receivers in various wavelengths.